a) Field of the Invention
The present invention is directed to a device for examining the eye, preferably the fundus of the eye, by means of an optical system and electronic sensors for image recording, wherein sectional enlargements of the recordings are possible by means of changing the imaging scale.
b) Description of the Related Art
According to the known prior art, the imaging scale in devices of the type mentioned above is usually changed by optical means which are swiveled into and out of the beam path in addition to or in exchange with one another.
The Laid Open Application DE 24 35 548 describes an optical system for photographing the retina with selectable imaging scale in which a plurality of optical changing systems which can be introduced into the beam path individually are provided in addition to the stationary objective systems. These changing systems are axially displaceable together with the aperture diaphragm in order to carry out focusing for eyes with defective vision. This technical solution is realized, for example, in the “FF 450” fundus camera by Carl Zeiss Meditec AG.
The disadvantage of this application consists primarily in the complicated adjustment of the optics and in the fact that the mechanical movement must be carried out very exactly. Since a complete set of optical components is required for every imaging scale, the structural size of the device in its entirety is substantially influenced by the size of the objective turret.
A simple technical solution for digital observation and documentation of the ocular fundus without eyepieces is offered by the “VISUCAM lite” fundus camera by Carl Zeiss Meditec AG. In this fundus camera, a black-and-white sensor and a color sensor are alternately laterally swiveled into the imaging plane of the system. In addition to the color photographs, black-and-white photographs are made using different monochrome techniques (red-free, blue, red) due to a higher sensitivity. To facilitate their comparison, the sensors have identical shape factors. By virtue of its many-sided possibilities for recording, analysis and aftertreatment, this solution provides a basic instrument for ophthalmologic practice and laser treatment.
The disadvantage in this device is that it does not provide for changing the optical imaging scale. In order to achieve this, an additional objective turret would be required. A correction of defective vision (also referred to as focusing) is carried out by a mechanical movement of the sensors along the optical axis.